Two New Bi 'hornyerofts
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TWO completely new models of Widely differing applications, and ,widespread additions to an existing range, are announced today by Transport Equipment (Thornycroft), Ltd.. Basingstoke, Hants. One of the two new models —the ML Mastiff 14-tons-gross fourwheeler—forms the subject of the road test report on pages 200-203 and the other is the MA Antar type of heavy-duty -iix-wheeled chassis designed primarily for oilfields use.
In addition to these new models the Trusty range, which formerly consisted only of an 18-ft. 4-in, wheelbase eightwheeler, has been extended to incorporate a tipper version of the eight-Wheeler and several normaland forward-control rear-wheel-drive sixand four-wheelers. these having been in production for several months.
Examples of some of these new models will be seen at Earls Court in a fortnight's time. Exhibits will include an MA Antar, an ML Mastiff of 16-ft. 6-in, wheelbase, a PK Trusty normal-wheelbase eightwheeler, an HL Swiftsure 17-ft, 6-in. wheelbase 6-tanner with 21-ft. 6-in, dropsided alloy body and new plastics cab. and a TEA Nubian 6 x 6 powered by a Thornycroft oil engine. On the Edbro13. and E. stand there wilt be a PK 14-ft. 6-in, wheelbase eight-wheeler with tipping body.
There are two basic MA Antar models. either of which may be supplied as 6 x 4 or 6 x 6 chassis. The models are the MA/KRN6, powered by the Thornycroft 11.33-litre 175 b.h.p. (gross) normally aspirated oil engin e, and the MA/KRN6/S, which has the turbocharged version of the same engine, the gross output of which is 216 b.h.p.
Although the MA vehicles are rated for a gross weight of 47+ tons solo, the chassis have been designed to a specification suggested by the Oil Companies c22 Materials Committee for 6 x 4 or 6 x 6 20-ton load carriers suitable for onor off-the-road operation. Thus the Thornycroft design has plenty in hand to meet the O.C.M.C. requirements, and is obviously suited to the type of work the committee had in mind when drawing up the specification.
The requirements drawn up by the 0.C.M.C. in their specification emphasized simplicity and robustness, with special stress on good unit accessibility, both for normal maintenance and for removal and replacement of parts in the field.
in other respects the specification was fairly broad. It suggested, however, a wheelbase of 23 ft. 9 in., and called for a six-cylindered oil engine of 12-15 litres developing at least 600 lb.-ft. torque at 1,000-1.200 r.p.m, and at least 175 b.h.p. at 1,800 r.p.m. for normal off-the-road working. For extreme conditions it was suggested that 700 lb.-ft. and 200 b.h.p. would be needed.
Other requirements were a minimum oil capacity of 6 gal., full-flow filters. vertical exhaust, 18-in, power-assisted clutch, synchromesh five-speed gearbox with adequate power take-off points,. auxiliary gearbox with full engine-torque power take-off for winch operation, hydraulic steering, air brakes, fully articulated suspension, twin rear tyres and a 50,00.0 lb. winch.
Thornycroft decided toconstruct a heavy vehicle for oilfields use to meet the 0.C.M.C. requirements, but at the same time not introducing the complication of the larger Antar tractor, which is, after all, mainly a military vehicle in its present application. The existing Big Ben, which is rated for 36 tons gross, would not permit the. clear 20-ton payload required.
The resulting chassis can be likened to a much lighter, simpler and less expensive version of the Antar incorporating Antar axles and transmission, Big Ben engine and steering," and a new chassis frame. At present it is offered only as a solo machine with normal control and a wheelbase of 23 ft. 6 in., leftor righthand drive being available.
As used in the MA/KRN6 chassis. the Thornycroft.KRN6 11.33-litre (69-cu.-in;) six-cylindered direct-injection oil engine has a net power output of 155 b.h.p. at 1,900 r.p.m., whilst its maximum torque output of 508 lb.-ft. occurs at 1,000 r.p.m. Fitted with an EberspRcher turbocharger (KRN6/S), the unit develops 200 net b.h.p. at the same governed speed, whilst the torque output is increased to 625 lb.ft. at 1,000 r.p.m. The blower adds little weightto the engine, but raises the net
torque by 23 per cent, and maximum net blip. by 29 per cent.
Blown or unblown, the engine has an 18-in.-diameter single-dry-plate clutch with an air servo. A wet sump gives a total lubricant capacity of 9 gal. and twin full-flow oil filters are incorporated. The cooling system, which is of 15-gal. capacity, is pressurized to 10 p.s.i. and an 18-in.-diameter six-bladed fan is installed.
Two 40-gal. fuel tanks are provided, one on each side of the chassis frame, and the fuel is lifted by a piston-type pump. It passes through a brass-disc primary filter and triple-paper-element main filters. A heavy-duty oilbath air cleaner is provided.
The main gearbox, which is mounted as a unit with the engine and clutch. is new and is used also in current Antars of the larger type. It is a constant-mesh design giving four forward speeds and reverse, and sliding dogs are fitted on all gears.
When used with the KRN6 engine its forward ratios are 6.07, 3.2, 1.69 and 1 to 1, with a reverse ratio of 10 to 1. With the blown engine the forward ratios are changed to 4.8, 2.73, 1.66 and 1 to I, with a 7.91-to-1 reverse. Provision is made for fitting a 30-h.p. power take-off on either side of the box.
Sliding dogs are used throughout the three-speed auxiliary box. This, too, is a new design, which is also to be installed in the larger Antars. The box is mounted separately from the main unit and gives Aatios of 1.728, 1 and 0.732 to 1. It is itted with a tower-type power take-off, .vith a separate reverse gear through vhich can be transmitted full engine .orque. The driving ratios given by this oower take-off are 0.97 to 1 forward and 173 to 1 reverse, and it is rated for 100 h.p.
It has a capacity for working with an 30,000 lb. winch and, as the drive is taken hrough the main gearbox, the winch peed can be adjusted by changing gear n the main box in the normal manner. For the 6 x 6 MA models the auxiliary tearbox incorporates an air-operated ront-wheel-drive engagement section (an:xample of which, but with manual peration, will be exhibited at the Show) vhich can be actuated irrespective of vhether high or low auxiliary ratios are .ngaged. The engagement dog is mounted on a helical spline to enable he drive to be engaged or disengaged rrespective of speed or terrain.
A two-piece propeller shaft with one flexibly mounted intermediate bearing takes the drive to the two rear axles of the Kirkstall bogie. This bogie is almost identical with that used in the heavier Antars and has double-reduction axles with overhead-worm and epicyclic gearing, all of which is in the central pots. The standard overall reduction ratio is 14.4 to I.
The bogie layout is such that rubberbushed torque and radius arms absorb all driving and braking torques and locate the axles longitudinally and laterally, thus relieving the springs of all stresses except vertical loading* The springs used at the back are inverted semi-elliptics, one on each side, and are 62 in long and 5 in. wide.
At the front a Kirkstall axle with rectangular-section beam and taperedroller thrust bearings is employed. In the case of the 6 x 6 versions a Kirkstall double-reduction front axle is fitted. The front suspension consists of two semielliptic springs, 48 in. long and 4 in. wide. The front-axle load rating is 10 tons, • whilst that of the rear bogie is 371 tons.
Marles cam-and-double-roller steering gear has integral valves for the Clayton Dewandre hydraulic steering servo which is standard on all MA chassis. The steering-box ratio is 28.5 to 1, and the turning circle has been calculated at 87 ft.
Air brakes are used. throughout the chassis, a split circuit being employed, with cam-operated leading-and-trailingshoe units at all wheels. All the brakes are 19 in. in diameter and the front facings are 4 in. wide, those at the rear being 7 in. wide.
Total frictional area is 1,044 sq. in., whilst the total drum area is 2,147 sq. in. Braking power is provided by a twincylindered compressor mounted on the engine, and a multi-pull hand brake is linked by rod to the rear brakes only.
The chassis frame of the MA is a most impressive structure. The side members consist basically of two channel section pressings, welded one inside the other, to form a fabricated channel 11 in. deep and + in. thick, with a flange width of 31 in.
The centre section of the frame is braced by 171-in.-deep flat gusset plates welded to the outside of the channels and having angle sections welded to their lower edges. This gusset extends from just behind the front axle to immediately ahead of the centre axle.
Further flitching and bracing members are employed in the vicinity of the bogie, whilst at the front end a channel-section sub-frame is bolted inside the main frame to form the front engine and bumper support. There are seven cross-members, the rearmost one being heavily braced for towing purposes, and fitted bolts are used throughout the frame assembly.
The side members are flat and parallel to each other throughout the length of the chassis and the maximum frame width is 3 ft. 1 in.
Standard tyres supplied with the MA chassis are 14.00-24 in. (20 ply), mounted on 10.00-24-in, three-piece wheels. Twin tyres are standard on the bogie axles. With . these tyres and standard axle ratios the maximum speed, allowing for 10 per cent, governor overrun, is 29+ m.p.h. with either engine.
A 24v electrical system is fitted and the engine carries a 51-in.-diameter 480W. dynamo. The battery is 154 amp.-hr. and a 6-in.-diameter axial starter is supplied. Instruments include two air-pressure gauges, oil-pressure gauge, ammeter, radiator thermometer, tachometer, speedometer and an odometer.
The overall length of the standard MA chassis is 36 ft. 5 in., including the front (Continued on page 203)